1. Field of the Invention
The present invention relates to a method, an apparatus and a display used for monitoring the operation of complex process control systems such as those used in nuclear power plants, and, more particularly, to a display which summarizes the status of functions or processes in the complex system in a manner which allows the operator to easily identify which processes require attention in the order in which attention should be given and at the same time monitor desired system parameters at a more detailed level to anticipate changes in status.
2. Description of the Related Art
Modern process control systems being installed in complex plants such as nuclear power plants do an excellent job of automatically or semiautomatically controlling a complex process within preset parameters even when there are disturbances in the plants. These control systems are capable of terminating the process when an emergency occurs; however, it is still desirable, and required in many situations, that a human operator make control decisions especially in emergency situations. It is possible for the modern automatic process control system to shut a plant down when an emergency occurs; however, human intervention may be able to solve a particular problem without plant shutdown if the problem is identified early enough in a degenerating situation.
In many complex processes, the operator is confronted with a vast amount of information that must be analyzed before appropriate action can be taken. In attempting to filter out unnecessary information and provide the operator with information appropriate to the problem, several different monitoring and display systems have been created. One such type is a status tree display system which illustrates the state of the process using a decision tree. A decision tree is a tool which defines a problem in terms of various combinations of parameters states which can occur. The parameters are analyzed sequentially with the active path through the tree being determined by the states of the parameters being assessed. An example of such a monitoring and display system is illustrated in U.S. Pat. No. 4,552,718 by Impink, Jr. et al.
Various methods of summarizing the results of status tree analysis have been proposed including what is called a status tree bar chart 8 which depicts the state of the functions being monitored, as illustrated in FIG. 1. This proposed status tree bar chart aligns one end of the bars on one side of a display and uses both color and words to identify functions and the degree or nature of the goal dissatisfaction by a particular process function. That is, words are used to name the function and describe the state whenever the function is not in a satisfactory state. The alignment gives the impression of continuous bars as well as the measurement of something with respect to a reference point. Since reference measurement points are not appropriate in such status displays, this aspect of the proposed display causes considerable confusion. The order of the bars on the proposed display of FIG. 1 is arbitrary and the functions which are in a satisfactory state are merely identified by an existing bar without words indicating which bar corresponds to which function. The proposed display requires the operator to memorize the location of each bar.